Proceedings Atmospheric Particulate Matter Variability during 2014 at Buenos Aires City (Argentina) Comparing † Ground-Based Measurements and Satellite Data Lara S. Della Ceca 1,*, María I. Micheletti 1,2 and Rubén D. Piacentini 1,3 1 Grupo Física de la Atmósfera, Radiación Solar y Astropartículas, Instituto de Física Rosario, CONICET—Universidad Nacional de Rosario, Rosario 2000, Argentina; [email protected] (M.I.M.); [email protected] (R.D.P.) 2 Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario 2000, Argentina 3 Laboratorio de EficienciaEnergética, Sustentabilidad y CambioClimático, IMAE, FCEIA, UniversidadNacional de Rosario, Rosario 2000, Argentina * Correspondence: [email protected]; Tel.: +54-341-485-3200 or +54-341-485-3222 † Presented at the 2nd International Electronic Conference on Atmospheric Sciences, 16–31 July 2017; Available online: http://sciforum.net/conference/ecas2017. Published: 17 July 2017 Abstract: Air pollution is a major environmental risk to health. In particular, exposure to high concentrations of small particulates (PM10 and PM2.5) is related to increased mortality and morbidity. In Argentina, only at Buenos Aires city (34.4° S 58.3° W), which together with the surrounding districts accounts for the 30% of the total country population, continuous measurements of air quality are carried out. Though ground-based stations provide very accurate PM concentration values, they have very limited spatial coverage and may not be sufficient to assess the level of population exposure. Satellite-based is a valid alternative to fill these observational gaps. In this work, the MODIS 3 km × 3 km AOD retrievals for 2014, for both Terra and Aqua, were employed to evaluate the spatio-temporal variation of atmospheric aerosols over Buenos Aires and its metropolitan area in a year period. The MODIS AOD dataset is validated using the AOD dataset reported by the CEILAP_BA AERONET station (34.5° S 58.5° W). Satellite data show some areas with higher AOD values throughout the year-period in which no PM monitoring is not actually being carried out. These areas correspond mainly to a west zone within Buenos Aires territory and two other areas, at west and south Buenos Aires districts. Buenos Aires local government and the surrounding districts should make an effort to expand the monitoring network in order to make it representative of the actual exposure to particulate matter of the whole population. Keywords: PM10; atmospheric aerosols; urban air quality; Buenos Aires; Argentina 1. Introduction Clean air is considered to be a basic requirement for human health and well-being. However, according to the last Air Quality report of the World Health Organization, more than 80% of people living in urban areas where air pollution is being monitored, are exposed to air quality levels that exceed the recommended limits [1]. The epidemiological evidence shows adverse effects of aerosols or particulate matter (PM) following both short-term and long-term exposures [2]. Particulate matter health effects is broad, but predominantly affect the respiratory and cardiovascular systems [3,4]. Moreover, particulate matter from traffic emissions has recently been classified as a Group I carcinogen by the International Agency for Research on Cancer [5]. Proceedings 2017, 1, 180; doi:10.3390/ecas2017-04152 www.mdpi.com/journal/proceedings Proceedings 2017, 1, 180 2 of 13 In most urban environments, particulate matter is primarily produced by mechanical processes (i.e., construction activities, road dust re-suspension and wind) and combustion sources. The concentration, size distribution and chemical composition of suspended particles varies substantially between cities around the world, depending on local geography, meteorology and specific PM sources. For this reason, local measurements are very important for a detailed knowledge of the characteristic of these particles. In Latin America, ground stations measuring PM are only available in 6 countries and extended, nation-wide PM monitoring networks only exist in Chile, Brazil, Colombia and Ecuador [6]. In Argentina, a continuous monitoring of PM is only available in Buenos Aires city. The Autonomous city of Buenos Aires is the capital and most populated city of Argentina, it accounts for approximately 10% of the total country population. It is surrounded by a large urban agglomeration that spreads north, south and west from Buenos Aires city constituting the ‘Gran Buenos Aires’ area. Gran Buenos Aires accounts for the 30% of the total country population and is the second metropolitan area more populated of South America and the southern hemisphere. Though no relevant nation-wide regulation on PM exists to protect the population in Argentina, an air quality law has been established in 2006 (Ley 1356, [7]) at Buenos Aires city, which regulates the prevention and control of air pollution in the city, including policies and urban planning in relation with the health, as well as the implementation of mitigation actions. This law established the limit values of PM10 and other pollutants. In the framework of this law, a monitoring network of air quality and meteorological variables was installed. During the last decades, measurements of air quality in Buenos Aires have been carried out by research institutions in an uncoordinated way, and consequently producing fragmented information. These research studies are focused on topics such as impact assessment of specific sources, characterization of multi-elemental aerosol composition, and source identification through receiver models [8–10]. Nowadays, a monitoring network composed of four stations that meet international quality standards to measure criteria pollutants provides air quality data for Buenos Aires city (http://www.agenciaambiental.gob.ar). Until some years ago, no consistent emission inventory is available for Buenos Aires. The first systematic attempt is described in [11]. This inventory refers to on-road mobile sources of Gran Buenos Aires reports emissions for the period 2000–2006 of greenhouse gases (CO2, CH4 and N2O) and criteria pollutants (CO, NOx, NMVOCS, PM and SO2) disaggregated by district and also presented in a grid of 1 × 1 km2 using a distribution algorithm described in [12]. Another inventory for stationary sources is described in [13]. According to these data, on-road vehicles are the main contributors for almost all of the pollutants in Gran Buenos Aires with the only exception of SO2 and CO2, for which stationary sources are dominant. The main drawbacks of these inventories is their static nature, they do not identify changes in sources emissions throughout seasons. Though ground-based monitors provide accurate measurements, they are often influenced by local emission sources. Moreover, their spatial coverage is limited and therefore may not correctly characterize the spatial-temporal distribution of aerosols in the city and the real exposure of its population [14]. Another way of studying the spatial distribution of contaminants is through remote sensing using satellite technology [15]. The most common parameter obtained by satellite sensors related to aerosols in the atmosphere is the Aerosol Optical Depth (AOD), also denoted as optical thickness, which measures the extinction of light due to dispersion and absorption by aerosols [16]. Several satellites provide global AOD coverage almost daily with different spatial resolutions (i.e., NOAA15, GOES, Suomi, Aqua, Terra). The main objective of our work is to study the space-time variability of particulate matter at Buenos Aires city for a year-period (2014) using ground-based measurements and satellite information. To our knowledge this is the first approach to study atmospheric aerosols dynamics at Buenos Aires metropolitan area using not only ground-based measurements but also satellite information. Proceedings 2017, 1, 180 3 of 13 2. Materials and Methods 2.1. Area of Study In accordance with the national census carried out in 2010, Gran Buenos Aires, is the most populated area in the country, with 12.806.866 inhabitants (INDEC, 2010). The Gran Buenos Aires is located on the western shore of the estuary of the Río de La Plata (Figure 1) and is composed of Buenos Aires city and 24 radially surrounding districts that are part of the province of Buenos Aires (Figure 2). Figure 1. Study area, Aeroparque meteorological station and PM10 ground-based stations location. Figure 2. Gran Buenos Aires districts. Data obtained from the National Meteorological Service for the 2003–2013 period indicate that Buenos Aires has a humid subtropical climate with four distinct seasons (Figure 3). As a result of Proceedings 2017, 1, 180 4 of 13 maritime influences from the Atlantic Ocean, the climate is temperate and extreme temperatures are rare. Summers are hot and humid. The warmest month is January, with a daily average of 24.7 °C, heat waves of short duration (less than a week) are common during summers. Winters are cold with maximun temperatures averaging 16.3 °C and lows 8.1 °C. July is the coolest month, with an average temperature of 11.5 °C. Relative humidity averages over 70%, which means that the ocurrence of moderate-to-heavy fogs during autumn and winter is common in the city. Spring and autumn are characterized by changeable weather conditions. Cold polar air from the south can bring cooler temperatures while hot humid air from the north bring hot temperatures. Total annual precipitation is aproximately 1.24 mm. Rains mainly occur during summer and spring. Winds are predominantly from the east and the wind speed is relatively higher in spring and summer compared to winter and fall (Figure 4). In Anex I a detailed wind rose for each month of 2014 is show. Figure 3. Climate data for Buenos Aires Aeroparque National Meteorological Service station at Aeroparque airport (2003–2013). Source: National Meteorological Service (www.smn.gov.ar). Figure 4. Wind rose (winds speed and direction average) for 2014 at the National Meteorological Service station located at Aeroparque airport (2003–2013). Source: National Meteorological Service (www.smn.gov.ar).